Telescoping camera crane

ABSTRACT

A telescoping camera crane has mechanical drive and camera platform leveling systems, allowing for water resistant or submerged operation. Telescoping sections of the crane arm are driven by a hydraulic system, for smooth and near silent extension and retraction movement. The telescoping sections of the crane arm have a slight upward curvature, to compensate for deflection the arm, thereby improving performance. Electronic and mechanical stopping systems allow the camera platform to be smoothly, accurately, and reliably positioned. Camera platform levelling and stabilizing systems keep the camera level.

This application is a Continuation-in-Part of U.S. patent applicationSer. No. 10/791,118, filed Mar. 1, 2004, and now pending, andincorporated herein by reference.

BACKGROUND OF INVENTION

The field of the invention is camera cranes.

Camera cranes are often used in motion picture and televisionproduction. The motion picture or television camera is typically mountedon a crane arm supported on a mobile base, dolly, or truck. The mobilebase may be pushed and steered by hand. Larger units, which have moreweight carrying capacity, and longer reaches, typically have electricdriving motors powered by onboard batteries. Some mobile bases alsoincluding conventional gasoline or diesel engines, may also serve asover the road vehicles.

Camera cranes generally have a crane arm supported on a base, with acamera platform at one end of the arm, and a counter weight at the otherend. The crane arm can be pivoted by hand to raise and lower the camera,and also to pan to the left or right side. A leveling system is oftenincluded to maintain the camera platform in a level orientation, as theelevation angle of the arm changes. Some mobile bases may include a selfleveling or an extendible center post or column, which the crane arm canbe mounted on.

With the development of high definition digital television cameras, andremote controlled motion picture cameras, filming can be achievedwithout a camera operator behind the camera. Rather, theremotely-controlled camera may be suspended on a crane arm, with thecamera operator monitoring the image captured by the camera via a remotemonitor.

Due to the variety of filming or video locations, the camera crane armshould advantageously be portable and lightweight. On the other hand,the arm must be rigid enough, when assembled, to resist bending andsagging, and to avoid excessive whipping motion of the camera duringcrane arm movement. Most camera cranes are made up from modular segmentsor sections, and have a fixed length. The segments are joined togetheruntil an arm of desired length is formed. With these types of arms, thelength can be changed only by adding or removing segments. This is atime consuming process, as segments and leveling arms are bolted intoplace or removed. In addition, each time the length of the arm ischanged, the arm must be rebalanced, by adding or removing counterweights. More importantly, crane arms having a fixed length cannotachieve various camera movements.

As a result, telescoping camera cranes have been developed. These typesof cranes have a telescoping arm that can extend and retract. Thisallows for a much broader range of camera movement. While existingtelescoping camera cranes have had varying degrees of success, existingdesigns have several disadvantages. Generally, the telescoping cameracranes available now use various electrical systems. Consequently, thesecranes tend to have performance problems if used in rain or wetconditions. Attempts to avoid or reduce these problems by wrapping ortenting the electrical components provide mixed results. Of course,these types of cranes also cannot be used underwater. In addition, thesetypes of cranes tend to be very large, heavy, and bulky. This makestransportation and set up time consuming and difficult. As productiontime is usually extremely expensive, time saving features are highlysignificant.

Moreover, under certain conditions, these types of telescoping cranescan cause unintended or undesirable camera movements, due to bending,flexing, twisting, or vibration of the crane arm. Noise generated frommoving parts in these types of cranes, when the arm is extended orretracted, can also disrupt filming or recording.

Accordingly, various engineering challenges remain in designing animproved camera crane.

SUMMARY OF THE INVENTION

After extensive research and development by the inventor, a noveltelescoping camera crane is provided with various new features andadvantages. In a first aspect, the camera crane has mechanical drive andcamera platform leveling systems. Consequently, the camera crane isessentially waterproof. While waterproof or water resistant enclosureshave been made for cameras, until now, little or no such paralleldevelopments have been made for camera cranes. Now, however, with theinventor's new crane, previously unknown and dramatic camera movementsand angles can be achieved. For example, using the present crane, thecamera can move down toward a water surface, and then pass through thewater surface into a submerged position, in a single continuousmovement, and without moving the mobile base, vehicle or dollysupporting the crane. In another example, the camera can approach, andmove directly through a waterfall, in a continuous movement, with nomovement of the mobile base required.

In a second and separate or independent aspect, the telescoping sectionsof the present crane are driven by a novel hydraulic system. Thisprovides exceptionally smooth and near silent extension and retractionmovement. This movement can also be precisely controlled. The hydraulicsystem includes a pair of hydraulic cylinders which alternately pull oncables, to extend and retract telescoping crane sections. This system ishighly compact, efficient, and waterproof.

In a third aspect, novel stop position systems are provided. In one stopsystem, stopping positions are set via an electronic control. In anotherstop system, valves are actuated directly by a component attached to andmoving with an arm section. These systems allow for highly reliable,repeatable and accurate camera positioning.

In another aspect, a camera platform levelling system uses cables tomaintain the camera platform in a level position, as the crane armpivots up or down in elevation. A cable tensioning or camera platformstabilizing system automatically compensates for backlash or stretchingof the cables. This allows the levelling system to constantly keep thecamera platform level.

Other aspects and advantages will be apparent from the followingdetailed description and drawings. The invention relies as well insubcombinations and subsystems of the elements described. For example,each of the features listed above can be used as an improvement in aconventional crane design. Alternatively, they may be used in variouscombinations with each other.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, wherein the same reference number indicates the sameelement in each of the views:

FIG. 1 is a side view of a novel telescoping crane, mounted on a mobilebase or vehicle, with the crane in the retracted position.

FIG. 2 is a side view of the crane shown in FIG. 1, with the arm nowfully extended.

FIG. 3 is a partial perspective view showing various components of thecrane arm shown in FIGS. 1 and 2.

FIG. 4 is a plan view of the crane arm shown in FIG. 1.

FIG. 5 is an enlarged side view of the crane arm shown in FIG. 1.

FIG. 6 is a plan view of the present crane arm in the fully extendedposition.

FIG. 7 is a side view thereof.

FIG. 8 is a partial section view taken along line 8-8 of FIG. 5.

FIG. 9 is a section view taken along line 9-9 of FIG. 6.

FIG. 10 is a partial plan view of the back end of the crane arm shown inFIGS. 3-7.

FIG. 11 is a side view thereof.

FIG. 12 is an enlarged plan view of the front end of the second armsection shown in FIG. 6.

FIG. 13 is a side view thereof.

FIG. 14 is an enlarged plan view of features shown in FIG. 4.

FIG. 15 is a side view thereof.

FIG. 16 is an enlarged side view of the front end of the crane arm shownin FIGS. 2 and 7.

FIG. 17 is a plan view thereof.

FIG. 18 is an enlarged plan view, in part section, of the crane arm inthe retracted position, as shown in FIGS. 4 and 5.

FIG. 19 is an enlarged side view, in part section, of the nose plate ofthe present crane arm.

FIG. 20 is a plan view thereof.

FIG. 21 is a top view of a roller bracket assembly for installation inthe front end of the second section, as shown in FIGS. 12 and 13.

FIG. 22 is a side view of the roller bracket shown in FIG. 21.

FIG. 23 is a perspective view diagram showing the second or a centersection drive cable connecting the counter weight carrier and the centertube.

FIG. 24 is a perspective diagram showing the top extending cable.

FIG. 25 is a perspective diagram showing the upper retracting cable.

FIG. 26 is a perspective diagram of the leveling system.

FIG. 27 is a schematic diagram of the hydraulic cylinder shown in FIGS.3 and 10 connected to a hydraulic control valve.

FIG. 28 is a side view of the hydraulic cylinder shown in FIG. 27.

FIG. 29 is a schematic diagram showing connections of the control valveto other hydraulic components.

FIG. 30 is a schematic diagram showing the entire hydraulic system ofthe crane arm shown in FIGS. 1-7. Bold lines indicate hydraulic lines.Light lines indicate electrical lines.

FIG. 31 is a top view of the base section of the hydraulic valve shownin FIG. 27, and further showing connections between ports of the basesection and the hydraulic cylinder shown in FIGS. 27 and 28.

FIG. 32 is a section view taken along line 32-32 of FIG. 31.

FIG. 33 is an enlarged section view of the valve assembly shown in FIGS.27 and 30.

FIG. 34 is a section view taken along line 34-34 of FIG. 33.

FIG. 35 is an enlarged section view of the piston within the hydrauliccylinder shown in FIG. 10.

FIG. 36 is a top view of the motor and valve assembly shown in FIG. 30.

FIG. 37 is a front view thereof.

FIG. 38 is a side view thereof.

FIG. 39 is a top view of a telescoping crane having an alternative drivesystem.

FIG. 40 is a schematic perspective of an alternative telescoping cranehaving a mechanical stopping position system, and automatic cameraplatform stabilizing or leveling systems.

FIG. 41 is a side view of the hydraulic stabilizing actuator shown inFIG. 40.

FIG. 42 is a top view of mechanical stopping position system shown inFIG. 40.

FIG. 43 is a section view taken along line 43-43 of FIG. 42.

FIG. 44 is a top view of another embodiment having a roll or dutch axisstabilization system.

DETAILED DESCRIPTION OF THE DRAWINGS

Turning now in detail to the drawings, as shown in FIGS. 1 and 2, atelescoping crane 30 is mounted onto a mobile base 32. The mobile base32 may be a truck or road vehicle, or a motorized special purpose cameracrane base or dolly. Typically, the mobile base 32 will have wheels 34which drive and steer the mobile base. Four-wheel drive and four-wheelsteering may be provided. For smaller scale cranes 30, e.g., up to about15 feet, the mobile base 32 may be unmotorized, and may be moved orpushed by hand. For larger versions of the telescoping crane 30, or whenrequired due to ground conditions or other use requirements, the mobilebase 32 can have electric motors, or internal combustion engines, fordriving the wheels 34.

As shown in FIGS. 1 and 2, the crane 30 is mounted on a column 36 on themobile base 32. The column 36 may be automatically leveled, as describedin U.S. Pat. No. 4,747,424, incorporated herein by reference, tomaintain the crane 36 in a level orientation as the mobile base 32 movesover uneven ground.

A U-shaped center post 46 is rotatably mounted on the column 36. Asshown in FIG. 8, a post 40 on the column 36 extends up through a lowercolumn bearing 42, and upper column bearing 43 secured within a postring 45 of the center post 46. A cap nut 44 is attached, e.g., threaded,onto the top end of the column post 40, to securely attach the centerpost 46 onto the column 36 of the mobile base 32, while still allowingthe center post 46 of the crane 30 to rotate. As shown in FIG. 5, thecenterpost 46 extends up at a rearward angle G, so that the tilt axle 70is offset behind the pan axis P by a distance DD. This offset, whichhelps to keep the center of gravity of the arm 35 centered over the panaxis bearings 42 and 43, varies with the arm design, and typically is1-3 inches. The corresponding angle G is generally 5-15 degrees. Anoptional potentiometer or angular position sensor 75 has a base attachedto the fixed or non-rotating column post 40, and a body linked to androtatable with the center post 46, to provide an electrical outputsignal to a controller, such as a control box 275 shown in FIG. 1.

Referring back to FIGS. 2, and 8, a crane arm 35 is supported on a tiltaxle 70 which is pivotably supported on the center post 46.Consequently, the crane arm 35 can rotate about a pan axis P, and canalso pivot about a tilt axis T shown in FIG. 8.

Referring to FIGS. 1-11, the crane arm 35 includes a first or outersection 52, a second or middle section 54, and a third or inner section56. As shown in FIG. 8, the first section 52 is supported on the tiltaxle 70 via an axle bearing 72. Fixed or non-moving trim weights 48 areplaced at the back end of the first section 52. The trim weights 48 mayor may not be needed or used, depending on whether non-moving weightfrom e.g., accessories, is added to the arm in front of the tilt axle.

A counter weight carrier or tray 50 is movable along the top of thefirst section 52, from a front or forward position F, when the arm 35 isfully retracted, as shown in FIGS. 1, 4, and 5, to a rear or backposition R, when the arm 35 is fully extended, as shown in FIGS. 2, 6,and 7. Moving or mobile counter weights 58 are attached to the counterweight carrier 50. As shown in FIGS. 3, 8, and 9, the counter weightcarrier 50 has top rollers or wheels 80 which roll on a roller track 82attached to the top surface of the first section 52. The counter weightcarrier 50 also has side rollers or wheels 84 which roll along the sidesof the roller track 82. The top rollers 80 support the weight of thecounter weight carrier 50 and moving counter weights 58, and allow thecounter weight carrier 50 to roll between the front and rear positionswith low force. The side rollers 84 keep the counter weight carrier 50aligned, side to side, on top of the first section 52, and secure thecounter weight carrier vertically against upward movement.

Referring to FIGS. 2, 6, 7, 16, 17, 19, and 20, a nose plate 65 isattached to a nose axle 196 pivotably attached at the front end of thethird section 56. A riser or extension 60 can be attached to the noseplate 65 with a mounting bolt 200 and a quick release position pin 202.

In the configuration shown, an extension 60 is used, and a remote camerahead 62 is attached at the front end of the extension 60. The camerahead 62 is described in U.S. patent application Ser. No. 10/782,034incorporated herein by reference. Of course, other camera heads may alsobe used. Alternatively, other camera support plates, risers, drop downsor accessories may be attached directly to the nose plate 65, with noextension 60 and/or camera head 62 being used. In the configurationshown, a camera 64 is attached to a camera platform on the camera head62. The camera head 62, if used, can provide controlled angular cameramovement about pan, tilt, and roll axes, independent of movement of thecrane arm 35. Referring to FIG. 19, the nose plate 65 has four or morepreferably equally radially spaced apart positioning holes 203. Theextension 60 and camera head 62 can be moved from the upright oroverslung position, shown in solid lines in the drawings, to an invertedor underslung position, as shown in dotted lines in FIG. 7, or to a 90degree position, as shown in dotted lines in FIG. 6, by loosening themounting bolt 200, withdrawing the spring-based position pin 202, thenturning the extension 60 to the desired position, releasing the positionpin 202, and retightening the bolt 200. These alternate positionsprovide added range of camera movement. In addition, the 90 degreepositions are useful in balancing the camera head 62.

The crane 30 has a hydraulic system 100 which provides the driving forcefor extending and retracting the crane arm 35. Referring to FIGS. 2, 3,and 27-30, the hydraulic system 100 includes a hydraulic cylinder 114attached to the top of the first section 52. A hydraulic cylinder cable118 extends through the hydraulic cylinder 114. A first end 120 of thecable 118 extends out through a rear cable seal 136, as shown in FIGS.27 and 35, and extends around a rear hydraulic cylinder cable pulley126, and is attached to the counter weight carrier 50 via a cable tie,clamp, or turnbuckle 128. Similarly, a second end 122 of the hydrauliccylinder cable 118 extends forward through the hydraulic cylinder 114from the piston 116, through a front cable seal 136, extends around afront hydraulic cylinder cable pulley 124, and is attached to thecounter weight carrier 50, also via a cable tie, clamp, or turnbuckle128. The cable seals 136 allow the cable 118 to slide through whilesealing hydraulic fluid within the cylinder 114.

The hydraulic cylinder cable 118 is attached to a piston 116 which ismovable back and forth within the hydraulic cylinder 114. As shown inFIG. 35, the piston 116 has front and rear piston crimp extensions 130which are tightly crimped onto the cable 118. Of course, otherattachments, such as screw threads, welding, adhesives, clamping, etc.,may equivalently be used. Referring still to FIG. 35, a piston seal orO-ring 132, backed by plastic or Teflon (Fluorine resins) seal rings134, provides a sliding seal between the piston 116 and the cylindricalinside walls of the hydraulic cylinder 114. The hydraulic cylinder cable118 advantageously has internal twisted bundles of high strengthfilaments, fibers, or wires, surrounded by a plastic or vinyl coveringor sheath. The ends of the cylinder 114 are sealed with an end cap orplug 136. An O-ring 137 in the end cap seals around the smooth coveringon the cable, while allowing the cable to slide in and out of thecylinder. As hydraulic fluid pressure is exerted against either thefront or back side of the piston 116, as described below, the piston 116moves through the hydraulic cylinder 114, correspondingly moving thecounter weight carrier 50 in the opposite direction. The hydraulicsystem 100 also includes other components for driving and controllingthe hydraulic cylinder 114. The design and operation of these otherhydraulic system components, which are generally located within ahydraulic system enclosure or housing 106 attached to the bottom of thefirst section 52, is described below. As shown in FIG. 27, the hydrauliccylinder 114, pulleys 124, 126 and cable 118 are provided as assembly125.

The crane arm 35 also includes a drive system 102, which extends andretracts the second section 54 and the third section 56, upon actuationof the hydraulic cylinder 114. Referring to FIGS. 3 and 23, a secondsection rear drive cable 140 (or pair of side-by-side cables) isattached to the top surface of the second section 54, via a cable tie,clamp or turnbuckle 146, adjacent to the back end of the second section54, extends around a rear pulley 144 attached to the back end of thefirst section 52 and is attached near the back end of the second section54. A second section forward drive cable 147 is attached to the counterweight carrier 50, extends forward around a front pulley 142, supportednear the front end of the top surface of the first section 52, and isattached to the top surface of the second section 54, near the back endof the second section 54. Consequently, as the counter weight carrier 50moves along the top of the first section 52, the second section 54 ismoved by an equal amount, in an opposite direction.

The drive system 102, as shown in FIGS. 3 and 24, also includes a topextending cable 152, and a symmetrical or mirror image or bottomextending cable 153, shown in profile in FIG. 8. As shown in FIG. 24,the back end of the top extending cable 152 is attached to a back wallof the first section 52 at a cable anchor or tie point 156. The topextending cable 152 extends forward, between the second section 54 andthe third section 56, runs around a top drive pulley 150, secured to theinside top surface of the second section 54 and is attached at the reartop surface of the third section 56, via a cable anchor or turnbuckle154. The top drive pulley 150 is mounted on the top inside surface ofthe second section 54, near the front end of the second section 54. Thebottom extending cable 153 has the same design. As the second section 54is extended out of the first section 52, via movement of the counterweight carrier 50 driven by the hydraulic cylinder 114, the drivepulleys 150 (one each on the top and bottom of the second section 54)pull the third section 56 out of the second section 54. Accordingly,when the hydraulic cylinder 114 is actuated to extend the crane arm 35,the third section 56 extends out of the second section 54 by the sameamount (and in the same direction) as the second section 54 extends outof the first section 52. This rearward movement of the counter weightcarrier 50, forces the forward movement of the third section 56 atdouble the (rearward) movement of the counter weight carrier.

The drive system 102 also includes a top retraction or pull back cable158, and a bottom retraction or pull back cable 159, as shown in FIGS. 8and 25. Referring to FIG. 25, the first or front end of the top pullback cable 158 is attached to the top inside surface of the firstsection 52, with a cable anchor or turnbuckle 162. The top pull backcable 158 then extends rearwardly, between the first section 52 and thesecond section 54, to a retraction pulley mounted on the top back end ofthe second section 54. For purposes of illustration, the bottomextension and retraction cables and pulleys are not shown in FIGS. 24and 25. However, they are duplicates of the top cable and pulley designsshown in FIGS. 24 and 25. Top and bottom cables and pulleys are used toprovide precise, smooth and more evenly balanced telescoping movement ofthe sections. However, single cable designs may also be used. Chains andsprockets may also be used in place of cables and pulleys.

The top retraction or pull back cable 158 extends around the topretraction pulley 160, passes through the slot or opening in the secondsection, and is attached to the top back end of the third section 56with a cable anchor or tie 156. The bottom pull back cable 159 has thesame design. Both retraction or pull back pulleys 160 and 161 areoriented in a plane P at an angle of 20-45 and preferably 30 degrees, toallow the pulleys to fit within a compact space between the second andthird sections, as shown in FIG. 8.

Referring momentarily to FIG. 25, as the second section 54 is retractedor pulled back into the first section 52, via the hydraulic cylinder 114moving the counter weight carrier 50, the top and bottom retractionpulleys 160 and 161 on the second section 54, move rearwardly with thesecond section 54, pulling the third section 56 back into the secondsection 54.

Turning momentarily to FIG. 7, with smaller versions of the crane arm 35(e.g., having an extended length of about 15 feet, as measured from thetilt axle 70 to the nose axle 196, the moving sections 54 and 56 may bestraight. For longer versions of the crane arm 35, the second and thirdsections 54 and 56 are advantageously formed with a slight upward radiusof curvature R. The radius R will vary, depending on bending anddeflection characteristics of the sections. Stiffer sections (i.e.,having a shorter length, thicker walls, or greater moment of inertia)will have less curvature, i.e. R will be greater. As one example, wherethe second and third sections are an 8 inch and a 6 inch square aluminumtube, each about 170 inches long (i.e., for a crane arm having anextended length of about 31.5 feet), R is preferably 8,000-20,000,10,000-18,000, or 13,000-15,000 inches. This upward curvature helps tocompensate for sagging of the arm 35 when loaded. With an averagepayload of about 150 lbs (including the camera 64, camera head or frame62 and extension 60), and with arm at a 30° elevation angle, the upwardcurvature R offsets the bending deflection, and the arm 35 is straight.With different payloads and elevation angles, the arm 35 will curveslightly up or down, but it will always be straighter than an armwithout any fault in upward compensating curvature R. Having the arm 35remain straighter improves performance because it helps to keep thecenter of gravity of the payload centered on the central axis of the arm35. Consequently, the arm 35 is less subject to eccentric loads ortorsional loading, resulting in a more stable camera platform. Inaddition, the straighter arm 35 is more easily kept in balance.

Referring to FIGS. 12, 13, 21, and 22, the third section 56 is supportedwithin the second section 54 by rollers 112 mounted on roller mountingplates or brackets 110. The roller brackets 110 are attached to theinside surface of the front end of the second section 52. Specifically,two roller brackets 110 are attached to the inside top, bottom, left,and right interior sides of the front end of the second section 52, fora total of 8 roller brackets. As shown in FIGS. 12 and 21, the rollerspread or footprint, i.e., the distance S between the front and rearrollers is minimized. This reduces the overlap between the secondsection 54 and the third section 56 when the crane arm 35 is fullyextended. Consequently, the crane arm 35, while typically having only 2moving sections, has an increased reach, while also remaining relativelycompact when retracted. The rollers 112 are preferably made of arelatively soft plastic or non-metal, preferably having a Shore hardnessof 70-90. This provides for smooth and quiet rolling between thesections. In addition, the rollers 112 help to absorb and reducetransmission of vibration between the sections. The rollers 112 andbrackets 110 are similarly used to telescopically support the secondsection 54 within the first section 52. For larger versions of the cranearm 35, the dimension S is increased, to better carry larger loads. Asexamples, for a crane arm 35 with about a 15 foot length (measured fromthe tilt axle to the nose axle) the dimension S is about 11 or 12inches. With a crane arm having a length of about 30 or 31 feet, thedimension S is about 23 or 24 inches. The brackets 110 areadvantageously bolted into position and fit tightly around the sectionthey support. As shown in FIGS. 12 and 13, cutouts, grooves, or recesses113 may be made in the sections, to provide clearance for the rollers112. For clarity of illustration, only one of the brackets 110, and onlysome of the rollers 112, are shown in FIG. 12, and they are omittedentirely from FIG. 13. The arm sections 52, 54, and 56 are preferablyhard anodized, to provide a hard surface which the rollers 112 roll on.Felt, or non-absorbing nitrile, rubber or plastic strips or wipersattached around the openings of the first section 52 and the secondsection 54 can be provided to wipe the second section 54 and the thirdsection 56, as the crane arm 35 extends and retracts.

A mechanical stop 108 at the back end of the third section 56 contacts abracket 109 on the second section 54 to provide a hard mechanical stopand to limit the extension of the third section 56 out of the secondsection 54. The extension of the third section 56 out of the secondsection 54 is also limited by the length of the extension cables 152 and153.

Referring to FIG. 8, the first section 52, second section 54, and thirdsection 56 are preferably square or nearly square aluminum tubes. In thedesign shown in the drawings, which provides an extension of travellength of approximately 112 inches, the first section is a 10×10¾ inchsquare tube, the second section is an approximately 8 inch square tube,and the third section is an approximately 6 inch (outside dimensions)square tube. Larger and smaller versions can of course also be made. Thesections may be formed as extrusions, weldments, bolted plates, or insimilar ways. Drain holes may be provided in the sections 52 and 54, toreduce buoyancy forces when they are submerged. As shown in dotted linesin FIG. 25, a fourth section 57 may also be used, as a third movingsection, to further increase the reach of the arm. The size, shape andnumber of telescoping sections, material selections, actuator (e.g.,hydraulic, electric, etc.) type, attachment techniques and accessories,are not essential to the invention and can be changed.

The crane arm 35 includes a leveling system 104 to maintain the noseplate 65, and any accessory attached to it, such as the extension orriser 60 and the camera head 62, in a horizontal or level orientation,regardless of the elevation angle M (shown in FIG. 2) of the crane arm35. The leveling system 104 consequently maintains the camera 64supported directly or indirectly by the nose plate 65, in a horizontalposition.

Referring now to FIGS. 3, 14, 15, 19, 20, and 35, the leveling system104, on the right side of the crane arm 35, includes a cable pulley 182rigidly attached to the center post 46. The back end of a spring cable184, which includes a spring 186, is attached to the cable plate 182.The front end of the spring cable 184 is attached to a rear levelingaxle assembly 188. The rear leveling axle assembly 188 is pivotablysupported on front end frame 180 attached to the front end of the firstsection 52. A first end 189 of a leveling cable 190 is attached to aninside pulley on the rear leveling axle assembly 188. The leveling cable190 extends rearwardly from the axle assembly 188, over an idler 194,around a rear leveling cable pulley 192 rotatably attached to the rearright side of the second section 54, and then extends forward under asecond idler 194 and is attached to a nose pulley 198 joined to the noseaxle 196. The same components are symmetrically provided on the leftside of the crane arm 35.

Referring to FIGS. 19 and 20, the leveling cable 190 wraps around thenose pulley 198, and is attached to e.g. clamped within the nose pulley198. Referring to FIGS. 2 and 3, the weight of the payload, e.g., thecamera 64, as well as any camera head 62 or extension 60, if used,exerts a downward or clockwise (in FIGS. 2 and 3) torque acting on thenose axle 196. Consequently, the leveling cable 190 and spring cable 184are typically maintained under constant tension. The spring 186 isselected with a spring constant to provide a level of flexibility in theleveling system 104. In the event that the nose plate 65, extension 60,or camera head 62 is moved forcefully into an overhanging surface orceiling, the spring 186 extends, allowing the nose plate 65 to movedownwardly (clockwise in FIG. 3) to reduce or avoid damage to the cranearm 35, extension 60, or camera head 62. The spring 186 may be omitted,or it can be locked out by a rigid cable link 185, or dampened with ashock absorber 187, shown in dotted lines in FIG. 14. During extensionof the crane arm 35, the rear leveling cable pulley 192, which isattached to the second section 54, moves forward at one-half the rate ofthe nose pulley 198 supported on the third section 56. Accordingly,tension in the leveling cable 190 is not affected by extending orretracting the crane arm 35. A clutch 195 may also be provided betweenthe nose axle 196 and the nose pulleys 198, to allow the nose plate 65to pivot downwardly under excessive momentary loading.

The hydraulic system 100 is shown in detail in FIGS. 3, 11, and 27-34.The hydraulic system 100 provides the motive force for moving thecounter weight carrier 50 and simultaneously extending or retracting thecrane arm 35. In normal and preferred operation, the crane arm 35 isbalanced. Forward, or upward movement of the payload is compensated byrearward or downward movement of the counter weight carrier 50 and themobile counter weights 58. Accordingly, the hydraulic system 100generally need only overcome forces of friction and inertia, to extendor retract the crane arm 35. As a result, the hydraulic system 100 iscompact and energy efficient. The components making up the hydraulicsystem 100, which are shown in FIG. 30, are preferably contained withinthe hydraulic system housing 106, except for the hydraulic cylinder 114which extends along the top surface of the first section 52.

As shown in FIG. 30, a pump 224 driven by an electric motor 220 chargesor pressurizes an accumulator 228. Instead of the motor 220, a hand pump233 may be used. The battery 222 can be charged by an external ACplug-in connection 237. Referring to FIG. 11, a cooling system 221,optionally including a recirculating liquid coolant, such as water,pumped through a radiator, may be provided around the pump motor, tocool the motor.

The accumulator 228 is connected via fluid lines to a valve assembly230, and also to a pressure switch 227, which automatically switches offthe motor 220 when a pressure limit is reached within the accumulator228. A pressure gauge 229 linked to the accumulator 228 is visiblethrough a window or opening in the enclosure 106. A battery 222 connectsto the motor 220 through a on/off switch 236 and the pressure switch227. An on/off indicator 235 is viewable through a window or opening inthe enclosure 106. A relief valve 240 joins into a T-fitting in the linelinking the accumulator 228 and the valve assembly 230, to relieveexcess pressure in the accumulator 228, and return hydraulic fluid to areservoir or tank 226. The reservoir 226 provides unpressurizedhydraulic fluid, through a filter 225 and a check valve 231 to the inletof the pump 224.

A valve shaft 232 extends through the valve assembly 230. Control knobs234 are provided at each end of the valve shaft 232, so that the valveassembly 230 can be controlled from either side of the crane arm 35.Referring to FIGS. 36-38, a chain or belt 290 connects a shaft sprocket296 on the valve shaft 232 with a motor sprocket 294 on a valve controlmotor 242. An adjustment and potentiometer idler sprocket 298 is alsoengaged with the chain 290, and is linked to a potentiometer 244. Thepotentiometer 244 and the valve control motor 242 are both connected toan electronic controller 248. The potentiometer 244 has a small cabletransducer attached to the counter weight carrier and provideselectrical signals to the controller 248 based on position, and speedand direction of movement of the counterweight carrier, which isproportional to the extension position of the arm 35. Stops limitrotation of the valve 230.

Referring to FIGS. 27, and 31-34, the valve assembly 230 includes avalve block 250 attached to a base 252. First, second, third, and fourthvalve pins 259, 261, 263, and 265 are positioned within first, second,third, and fourth bores 258, 260, 262, and 264 in the valve block 250and base 252, forming four valves. The first bore 258 connects with thethird bore 262 via a first or rear drive port 254, as shown in dottedlines in FIG. 31. Similarly, the second valve bore 260 connects with thefourth valve bore 264 via a second or front drive port 256, also shownin dotted lines in FIG. 31. Plugs 261 seal drill openings made duringmanufacture, to provide right angle bends in the internal ports. Thefirst or rear drive port 254 of the valve assembly 230 is connected to arear port 216 of the hydraulic cylinder 114. The second or front driveport 256 of the valve assembly 230 is connected via a hydraulic line toa front port 218 of the hydraulic cylinder 114, as shown in FIGS. 27 and31. A high pressure inlet port 266 is connected via a hydraulic line tothe accumulator 228. A low pressure inlet port 268 in the valve block250 is connected via a return hydraulic line to the reservoir 226. Eachof the valve pins 259, 261, 263, and 265 is biased upwardly or into aclosed position via a spring 270. In the up or closed position, a headon the hardened valve pin seals against a hardened valve seat 274pressed and/or swaged into the valve body at the lower end of each bore.A valve piston 276 is centered on a shoulder and threaded onto each ofthe valve pins. This design provides a highly reliable and durable sealof each bore which is very resistant to leaking, even at high pressures.The springs 270 bias the valve pistons 276 against cam lobes 272 on thevalve shaft 232. Small clearances assure seating of the valve pins inthe valve seat, and provide a detent. The cam lobes are preferably 90degree offset circles, to provide smooth (sinusoidal) movement of thevalve pins. As shown in FIG. 33, O-rings 278 and 280 seal the pin bores.

The valve shaft 232 is set up with stops that limit rotation to about+/−85 degrees. This allows for complete valve control, without the needto remove and reposition the users hand on the control knob 234.Ergonomics are improved. Using a potentiometer 244 having a 170 degreerange of movement in one direction, plus 170 degrees in the otherdirection, and 2:1 tooth ratio between the shaft sprocket 296 and theidler 298, allows for use of the potentiometer over its entire range,for greater control sensitivity. As the valve shaft 232 is turned,either manually by gripping and turning the control knob 234, orautomatically via the valve control motor 242 and electronic controller248, the ports in the valve assembly 230 are opened and closed, tocontrol movement of the piston 116 within the hydraulic cylinder 114.For example, with the valve shaft 232 at a zero degree position, allports are closed and no movement of the crane arm occurs. To begin toextend the crane arm 35, the valve shaft 232 is turned (clockwise inFIG. 30). This opens first and fourth valves, connecting the rear port216 to the accumulator and simultaneously connects the front port 218 tothe reservoir, through the valve assembly 230. Hydraulic fluid pressureon the back of the piston 116 exceeds the fluid pressure on the frontsurface of the piston, causing the piston 116 to move forwardly (to theright in FIGS. 3, 27, and 30. The hydraulic cylinder cable 118 is drivencounter-clockwise (in FIG. 30). The counter weight carrier 50, which isattached to the hydraulic cylinder cable 118 moves rearwardly upon thetop surface of the first section 52. Referring momentarily to FIG. 23,as the counter weight carrier 50 is driven rearwardly, the secondsection drive cable (or pair of cables) 140 drives the second section 54forwardly. Referring momentarily to FIG. 24, this forward movement bythe second section 54 simultaneously drives the third section 56forwardly, via the forward movement of the third section drive pulley150 and 151 (both attached to the second section 54) acting on the topand bottom extending cables 152 and 153. As a result, the third section56, moves outwardly to the desired camera position. To reverse directionand retract the crane arm 35, the valve shaft is turned back (counterclockwise in FIG. 30) through the stop or closed position. This closesthe first and fourth valves and then opens the second and third valves.Now, the hydraulic connections to the hydraulic cylinder are reversed,driving the piston in the hydraulic cylinder in the reverse directionand retracting the arm. The speed of extension and retraction willincrease with increasing movement of the valve shaft away from the zeroor closed position, due to the shape of the cams. Since the valveassembly to 30 is pressure compensated, only small amounts of force arerequired to turn the valve shaft 232 and open and close the valves.

In use, the crane 30 is shipped to the filming location in the retractedposition. The trim weights 48, and the mobile counter weights 58, andany riser or extension 60 and camera head 62 are preferably separatedfrom the camera crane 30 and transported individually to maketransportation easier. At the filming location, the crane 30 is attachedto a mobile base 32. The riser or extension 60 and the camera head 62(if used) are attached to the nose plate 65. The camera and anyaccessories are attached to the camera platform. Mobile weights 58 areadded to the weight carrier until the arm is balanced. The center ofgravity CG of all of the moving elements is therefore then fixed, andremains on the pan axis P shown in FIG. 15, whether the arm is extendedor retracted or in between. Correspondingly, the center of gravity CG ofthe arm 35 also remains centered over the pan bearings 42 and 43. As aresult, during panning movement, the weight load of the arm remainscentered on the bearing. Deflection during panning of the center post46, or of the frame or tires of the mobile support, is reduced oravoided entirely. This provides a more stable support for the camera. Ifneeded, trim weights are added to precisely balance the crane arm 35.While the trim weights will typically be added at the back end of thearm, for some uses, they may also be attached near the front end of thearm.

The camera head 62, if used, is balanced using known techniques,conveniently by moving the camera head 64 into a 90 degree position, asshown in FIG. 6. The hydraulic system 100 is charged, preferably byplugging wall current into the connector or plug 237 within theelectrical system of the hydraulic system 100. Alternatively, power fromthe battery 222, controlled by the switch 235 is used to power the motor220 driving the pump 224. As the hydraulic system 100 operates with onlysmall volumes of hydraulic fluid, the accumulator 228 can be quicklycharged. The crane 30 is then ready for use in filming.

The camera 64 is brought to the desired position by pivoting the cranearm 35 about the pan axis P shown in FIG. 8, and by pivoting the cranearm 35 about the tilt axis T. These pivoting movements are typicallyperformed manually. As the arm 35 is balanced, little or no liftingforce is required, and manual or hand force is required only to overcomefriction and inertia. Alternatively as shown in FIG. 1, crane arm panand/or tilt axis motors or actuators 74 and 76 can be provided on themobile base or crane arm to perform these operations. The actuators 74and 76, as well as the hydraulic control valve assembly 230, mayoptionally be remotely controlled, via a control box 275 connected toeach of them via a wired or wireless connection. This allows the entirecrane 30 to be remotely controlled. Pan and tilt sensors 75 and 77(shown in FIGS. 8 and 2) provide rate, direction, and/or positioninformation to the control box 275.

The telescoping movement of the crane arm 35 is initiated by turning thecontrol knob 234. This actuates the valve assembly 230, supplyinghydraulic fluid to the hydraulic cylinder 114 to drive the piston 116,counter weight carrier 50, and in turn the second and third sections 54and 56, as described above. The controller 248 can be set up orprogrammed to actuate the valve control motor to operate the valveassembly. This allows the crane arm 35 to automatically move topre-selected positions, or to perform pre-programmed movements. (Theremote control box 275 may be similarly programmed, with positions ormovements (pan, tilt, telescope extend/retract) for the entire crane 30,and/or the camera head 62.)

As shown in FIG. 1, using the camera head 62 allows the center ofgravity CGP of the payload (typically the camera 64 and head 62) to bepositioned on a horizontal central axis CC (shown in FIGS. 3-5) of thecrane arm 35, as the sections or segments of the camera head 62 areadjustable. Positioning the center of gravity CGP of the payload on thecrane arm center line CC reduces or eliminates twisting or torsion ofthe crane arm 35 during rapid arm movements. Accordingly, the camera canbe quickly moved from one position to another, without excessivegeneration of vibration or resonance in the arm 35. This provides a morestable camera support.

Referring to FIGS. 1 and 2 the counter weight carrier is movable alongsubstantially the entire length of the first section 52. With the cranearm 35 in the retracted position, the counter weight carrier 50 is infront of the center post 36. As the range of movement of the counterweight carrier 50 is increased, in contrast to prior designs, fewermobile counter weights 58 are needed for balancing. Accordingly, theweight of the entire crane 30 is reduced. This allows for easiertransportation and setup. In addition, less force is needed to move themobile counter weights, reducing the size and weight of the hydraulicsystem. The crane arm 35 is always maintained in balance, as the centerof gravity CG of the arm is fixed. Even when the counter weight carrier50 moves forward of the center post 46, the crane arm 35 remainsbalanced, with the CG forward of the tilt axle. Referring to FIG. 9,counterweights 59 may be provided on the top of the counterweightcarrier 50, in addition to the sides of the counterweight carrier, toimprove balancing characteristics under varying conditions.

The hydraulic system 100, including the hydraulic cylinder 114, and thevalve assembly 230 also form a separate inventive subsystem having otheruses. This subsystem may be used in other equipment where an actuatorapplies force over a relatively long distance. In a basic form, thehydraulic system includes a piston slidable within a hydraulic cylinder.A first cable is attached to a first end of the piston and a secondcable is attached to a second or opposite end of the piston. The cablesextend through the hydraulic cylinder and pass out of the hydrauliccylinder through cable seals. The cable seals allow the cables to slideinto and out of the cylinder, while maintaining pressurized hydraulicfluid within the cylinder. The cable seals optionally may also provide awiping action on the cables, so that the cable sections outside of thecylinder are substantially dry and free of hydraulic oil (even thoughthe sections of the cables within the cylinder are immersed in orsurrounded by hydraulic oil). However, the wiping action is notessential. Since the piston can move through substantially the entirelength of the cylinder (while pulling the first or second cable withit), a very long actuation length or stroke is provided, in alightweight and compact design. The first and second cables canoptionally be formed as single cable loop. To better provide a sealagainst the cables sliding through the cable seals 136, the cables 120,122 may be formed with a smooth outer coating, sheath or jacket (ofe.g., plastic) surrounding a core of high strength fibers (of e.g.,steel, Nylon, etc.)

The valve assembly 230 also forms a separate inventive subsystem usableas well in other types of equipment and machinery, where precisehydraulic movements are used and with no leakage, even at highpressures.

The crane arm 35 can be more safely used in wet areas and environments,because it can operate entirely on low voltage battery power, or canoperate without any electrical power at all. While the hydraulic systemadvantageously includes a battery and motor, these are low voltagecomponents (typically 12, 24 or 36 VDC). The hydraulic system can alsobe operated using the hand pump. The accumulator, once charged withhydraulic pressure, can also drive the crane arm 35 through severalextension/retraction cycles, without any pumping or external power. Thelow voltage battery can be periodically recharged when the crane arm 35is not in use. Alternatively, it can be quickly replaced with a freshbattery, while the crane arm is in use. This avoids the need forconnecting 110 VAC or 220 VAC line current electrical cables to thecrane arm (as is often required with existing crane arms). As a result,safety relating to proper equipment grounding or shock hazards arereduced, since the crane arm 35 does not require line current orexternal grounding. Thus, in wet environments, the ability to operateonly on battery power, or hand pump power, is a significant improvement.The need for inverters and transformers associated with use of 110 or220 VAC power, is also avoided. In addition, since external electricalpower is not needed, the entire crane and mobile base can operate morefreely, as the drag and wheel obstacles created by external electricalcables is avoided. Moreover, the 12, 24 or 36 VDC electrical system ofthe crane 35, if used, is compatible with the electrical power systemsof most cameras and remote camera heads.

FIG. 39 shows an alternative crane arm extension/retraction drive system300 which can be used instead of the drive system 100 shown primarily inFIGS. 26-28. The drive system 300 has a first or retracting linearactuator 302 and a second or extending linear actuator 304. Theactuators 302 and 304 may be hydraulic, electric, pneumatic or use otherdrive means suitable for moving the counterweight carrier 50. Non-linearactuators for moving the counterweight carrier 50 may also be used,including rotary actuators or winches acting directly to pull on a cableattached to the counterweight carrier 50. In the embodiment shown inFIG. 39, the actuators 302 and 304 are linear hydraulic actuators. Whileother types of actuators may be used, hydraulic actuators may beadvantageous because they are quiet, precisely and relatively easilycontrolled, compact, reliable, and can be remotely powered via ahydraulic system located away from the actuators themselves. Hydraulicsystems are also waterproof.

Referring still to FIG. 39, where the actuators are hydraulic, each ofthe actuators 302 and 304 has a cylinder 306 attached or fixed in placeon the first section 52, and a piston or ram 308 moveable into and outof the cylinder via hydraulic power. The cylinder 306 of the firstactuator 302 is attached towards the back end of the first section 52.The cylinder 306 of the second actuator 304 is attached towards thefront end of the first section 52.

The first actuator 302 acts as a retraction actuator as it pulls thecounterweight carrier forward (to the position shown in solid lines inFIG. 39) which causes the arm to retract, as described above withoperation of the drive system 100. The second actuator 304 acts as anextension actuator as it pulls the counterweight carrier 50 rearwardlytowards the back of the first section 52 (to the position shown indotted lines in FIG. 39) which causes the arm to extend.

A retraction actuator pulley 326 is rotatably supported on a clevis atthe end of the piston 308 of the first actuator 302. A retraction cable324 has a first end 325 fixed or clamped near the front end of the firstsection 52. The retraction cable 324 runs or extends rearwardly from thefirst end 325, wraps around the pulley 326, runs forward and wrapsaround a forward idler pulley 322, then runs rearwardly and is attachedto the counterweight carrier 50. The idler pulley 322 is rotatablyattached to, and fixed in place on, the top surface of the first section52, adjacent to the front end of the first section 52. As a result, whenthe actuator 302 retracts or pulls back, the counterweight carrier 50 ispulled forward, to the position shown in solid lines in FIG. 39. Thiscauses the arm 30 to pull back or retract, as described above relativeto operation of the drive system 100.

Symmetrical with retraction components described just above, anextension actuator pulley 310 is rotatably supported on a clevis orother fitting at the end of the piston 308 of the second actuator 304.An extension cable 314 has a first end 315 fixed or clamped near theback end of the first section 52. The extension cable 314 runs orextends forwardly from the first end 315, wraps around the pulley 310,runs rearwardly and wraps around a rear idler pulley 316, then runsforwardly and is attached to the counterweight carrier 50. The idlerpulley 316 is rotatably attached to, and fixed in place on, the topsurface of the first section 52, adjacent to the back end of the firstsection 52. As a result, when the actuator 304 retracts (i.e., when thepiston 308 is withdrawn into the cylinder 306), the counterweightcarrier 50 is pulled rearwardly, towards the back of the first section52, to the position shown in dotted lines in FIG. 39. This causes thearm 30 to pull extend as described above relative to operation of thedrive system 100. Chains and sprockets can alternatively be used inplace of pulleys and cables. The term pulley as used here includessprockets and the term cable as used here includes chains. The termcable here includes flexible elements having a single or multiplestrands, wires or fibers.

FIG. 40 shows an alternative embodiment 340 similar or the same as inthe Figures described above, and optionally including one or both of anose plate or camera platform angle stabilizing system 342, and amechanical stopping position system 400. The cables 184 and 190 whichmechanically level the nose plate 65 and camera head 62 are subject toslight stretching/contracting as the arm extends and retracts. Thisintroduces backlash into the leveling system 104 and can cause the noseplate 65 to deviate slightly from level with telescoping movement of thearm. The term backlash here means the characteristics of the levellingsystem that cause the camera platform to deviate from level, when thearm extends or retracts. Stretching of the cables is the main source ofbacklash, with smaller amounts of backlash arising from strain of othercomponents, and from other sources. The stabilizing system 342 reducesor prevents this deviation, and helps to maintain the nose plate, andthus the camera, in a level position, during telescoping arm movement.

The stabilizing system 342 is generally symmetrical on both sides of thecrane arm shown in FIG. 40. As shown in FIGS. 40 and 41, the stabilizingsystem 342 includes a cable tensioning assembly 344 attached to eachside of the arm on a mounting bracket 345. The cable tensioning assembly344 on the right side of the arm (shown in FIG. 40) acts on the rightside cable 184. The cable tensioning assembly 344 on the left side ofthe arm (not shown) acts on the left side cable 184. The cabletensioning assemblies or means 344 exert a downward force on the cables184, when the arm extends. The cables are released when the armretracts. The position of the cables 184 during extension is shown indotted lines in FIG. 41. The position of the cables 184 duringretraction is shown in solid lines in FIG. 41. The cable tensioningassembly can exert force on the cables in various ways, including viamechanically or electrically driven motors or actuators.

FIG. 41 shows a hydraulically driven cable tensioning assembly 344,suitable for use with a hydraulically driven crane arm. As shown in FIG.41, a hydraulic cable tensioning assembly 344 has a piston 348 moveablein a cylinder 350. A piston adjuster 362 may be provided to adjust theposition of the piston. A cable plate 352 is attached to the piston 348and is positioned on or around the cable 184. No spring 186 is used. Inthe stabilizing system 342 as shown in FIG. 41, the ports 354 and 356are directly connected to the valve assembly 230 or to the hydrauliclines leading to ports 214 and 216. Consequently, the tensioningassembly 344 operates in parallel with and in proportion to hydraulicpressure supplied to the drive system 102 or 300.

In use, as the valve assembly 230 is actuated to extend the arm, fluidflows into the drive system 102 or 300, and also generallysimultaneously to the cable tensioning assemblies 344. The piston 348 ineach cable tensioning assembly 344 is forced down. This deflects thecable 184 from the position shown in solid lines, to the position shownin dotted lines, in FIG. 41. The amount of deflection needed to maintainthe nose plate continuously level will vary depending on the payload,the elastic characteristics of the cables, and other factors. The amountof deflection can be adjusted as desired using the position adjuster362. The movement profile and timing of the piston 348 can be selectedvia control of fluid flow to the cylinder 350. By deflecting the cables184, the cable tensioning assemblies compensate for backlash in theleveling system caused by stretching of the cables when the arm extends.According the nose plate 65 and any camera head 62 and camera 64 remainsubstantially level at all times. As shown in FIG. 43, to reducebacklash in the drive system, multiple cables 158 may be used, in placeof the single cable 158 shown in FIG. 8.

The cable tensioning assemblies hold the cables 184 in the deflectedposition, until the arm is retracted. During retraction, the flow ofhydraulic fluid to the cylinder 350 is reversed, moving the piston backup. The cables 184 return to the original position shown in solid linesin FIG. 41. Typically, the cable tensionings will deflect the cable fromabout 0.1 to about 0.6 inches, more typically about 0.2-0.4 inches. Thestabilization system can also be equivalently designed to deflect thecables 184 up instead of down. If the flow of hydraulic fluid to thecylinder 350 in each cable tensioning assembly 344 is made proportionalto the flow of hydraulic fluid to the cylinder 114, 302 or 304, then theaction of the cable tensioning assemblies is automatically matched tothe extension/retraction movement of the arm.

In an alternative system 360, shown in FIG. 40, a sensor or gyro 390 mayoptionally be provided on the nose plate 65, camera head 62 or thecamera 64, with the sensor 390 linked to an electronic valve controller374. The link may be wireless or via wires. The sensor 390 sensesposition relative to gravity and provides a position signal to theelectronic valve controller 374. The electronic valve controllercontrols operation of a cable tensioning valve 385. The valve 385 isconnected via hydraulic lines to hydraulic system ports 384 and 386, andto the cylinder 350 of each tensioning assembly 344. The ports 384 and386 are connected directly to the accumulator 228, and to the returntank or reservoir 226. Consequently, the ports 384 and 386 are alwayssupplied with hydraulic fluid pressure (so long as the accumulator ischarged), regardless of the position of the valve assembly 230 (FIG.30).

The electronic valve controller controls the valve 385 to provide flowof hydraulic fluid to the cable tensioning assemblies 344, which deflectthe cables 184 as needed, to maintain the nose plate 65, and hence thecamera 64, in a level position. The sensor 390 and control loop to theelectronic valve controller 374 may be especially useful when the craneis supported on a moving platform, such as moving land vehicle, orwatercraft. Where the platform or vehicle is constantly moving (e.g.,the rocking movement of a floating vehicle or platform), the camera 64may be constantly maintained in a level position, via constant activecontrol of the nose plate position, via the sensor 390 and electronicvalve controller 374. With this automatic leveling system, theelectronic valve controller 374 can continuously control operation ofthe cable tensioning assemblies 344, whether the arm is stationary ormoving (i.e., extending or retracting). The system 360 operates to keepthe camera level, regardless of operation of the drive system 102 or300.

The stabilizing system 360 also operates independently of thestabilizing system 342. The stabilizing system 342 operates tocompensate for backlash inherent in the crane arm components (primarilythe stretching of cables). The system 342 generally will be included aspart of the crane itself.

The stabilizing system 360 operates whenever the arm changes directionof movement, and provides a predetermined amount of cable deflection.The stabilizing system 360, on the other hand, generally may be includedas part of the crane itself, or may also be provided separately as anaccessory or add on package. The system 360 operates to compensate forexternal forces (such as buoyancy, inertia, acceleration, etc.) actingto move the camera platform out of level. When on, the system 360operates continuously to keep the camera level, regardless of whetherthe arm is extending, retracting or stopped.

For certain filming sequences, the camera 64 and camera head 62 (ifused) may be submerged under water. When submerged, buoyancy forces willchange the loads on the crane arm and on the leveling system 104. Use ofthe sensor 390 and electronic valve controller 374 system allows theleveling system 104 to keep the camera level, regardless of the buoyancyforces present during underwater filming.

As shown in FIGS. 30 and 40, in addition to, or as an alternative tocontrolling telescoping movement of the crane arm via the control knob234, a remote control unit 370 may also be provided. The remote controlunit 370 is linked to the electronic valve controller 248 via a wired orwireless link 372. A hand control 376, such as a rocker switch,joystick, etc. is used to control the direction and speed of telescopingarm movement. Stop positions may also be selected by adjustingelectronic stop positioners 378 on or in the unit 370. Using an armposition signal from the potentiometer 244 and the stop position valuesselected via stop positioners 378 on the remote control 370, the valvecontroller 248 actuates the valve 230 so that the arm stops at theselected positions. Accordingly, the limits of telescoping arm movementcan be set electronically using the unit 370 and electronic valvecontroller 374, or by using the mechanical stop position system 400described below. Of course, stop positions may also be setelectronically via the electronic valve controller directly, with orwithout use of the remote control unit 370.

A mechanical stop position system may be used to temporarily selectextended and retracted limits of travel which are less than the totalavailable range inherent in the crane arm. Setting such temporary frontand back stop positions may be useful in filming sequences requiring thecamera to located at a precise position, moved away, and then returnedback to the that position. The mechanical stop position system usesmovement of a component of the arm to control the arm drive system, sothat telescoping movement of the arm stops at a desired position. Thespecific drive system (hydraulic, electric, pneumatic, etc.), and thespecific moving component of the arm used, may vary with designparameters.

FIGS. 40 and 42 show a mechanical stop system 400 that works with ahydraulic drive system such as 102 or 300. The counterweight carrier 50is selected as the moving arm component which operates the stop system400. As shown in FIG. 40, the stop system 400 has a front bar or rail402 supported by supports 410 on the top surface of the first or outersection 52. A cam or angle surface 404 adjacent the front end of thefront bar 402 faces a hydraulic stop valve 406. The front bar 402 ismoveable in a front/back direction, over a distance sufficient for thecam 404 to operate the stop valve 406. Back up rollers 408 support theback surface of the bars 402 and 414.

Referring still to FIGS. 40 and 42, a rear bar 414 similarly has a rearcam 416 for operating a rear hydraulic stop valve 418. A tension spring412 connects the front and rear bars. Referring now to FIGS. 40 and 43,a carrier pin 420 extends down from the bottom surface of thecounterweight carrier 50. As the carrier 50 moves towards the back ofthe arm (as the arm telescopically extends outwardly), the carrier pin420 contacts a pin stop 422 attached on the rear bar 414, moving therear bar 414 to the rear, against the force of the spring 412. As thisoccurs, the rear cam 416 moves into engagement with a, pin or othercomponent of the rear stop valve 418, gradually closing the valve 418,and stopping telescoping arm movement. The shape of the cam or anglesurface 416 is advantageously selected to provide a gradual or featheredstopping movement. This avoids abrupt stopping movements. The pin stop422 can be secured at any position along the rear bar 414 (e.g., with athumbscrew, wingnut, etc.) to select the front or extended positionstopping position of the arm. Front and rear bar stops 425 limit therearward and forward movement of the front and rear bars 402 and 414respectively. The bar stops 425 are positioned to limit bar travel toabout 1-4 or 2-3 inches, a dimension comparable to or slightly longerthan length of the cam or angle surface 404 or 416.

When the arm is retracted, the carrier pin 420 moves forwardly with thecarrier 50. The spring 412 pulls the rear bar forward, disengaging thecam 416 from the stop valve 418, and returning the rear bar 414 to itsoriginal position. As the arm continues to retract, a similar stoppingoperation is performed via the pin 420 acting on the pin stop 422 on thefront bar 402.

As shown in FIG. 30, the mechanical stop system 400 operatesindependently of the electronic valve controller 248 and the valve 230.Consequently, in the event of failure of the electronic valve controller248, or electrical power failure, the mechanical stop system isunaffected and continues to operate. Some filming sequences may requirerapid camera movement to a position close to an actor, or close tomoving or dangerous props or equipment. To even more reliably stop thecrane arm at a desired position, a stop position can be set via both theelectronic stop positioner 378, and the mechanical stop system 400.

An optional roll or dutch angle control system 450 is shown in FIG. 44.The extension or riser 60, for example as shown in FIG. 20, is modifiedto attach to a gear sector plate 452. The plate 452 is pivotablysupported on a bearing 454 on the nose plate 65. A worm gear 456 mesheswith a gear sector on the plate 452. The gear is driven by a motor 458.A sensor 392 detects the position of the extension or riser 60, andprovides a signal to a motor controller 375 (FIG. 44), via a wired orwireless link 394. The motor controller 375 may be included with or partof the electronic valve controller 374 (which will typically be locatedwithin the housing or enclosure for the hydraulic system 100, at theback end of the arm). Alternatively, the motor controller 375 may beseparately provided (along with the sensor 392 and motor 458) andattached elsewhere on the arm. The motor controller 375 controls themotor 458 to pivot the gear sector plate 452, and hence the extension orriser, and the camera, to maintain a level or zero roll angle. Similarcontrols may be used to maintain a constant pan angle as well.

Thus, a novel camera crane, hydraulic system, actuator and valve havebeen shown and described. Changes and substitution may of course he madewithout departure from the spirit and scope of the invention. Theinvention, therefore, should not be limited, except to the followingclaims and their equivalents.

1. A telescoping camera crane comprising: a first section; a counterweight carrier moveable relative to the first section; a second sectiontelescopically extendible out of the first section; a first actuatorlinked to the counterweight carrier, for moving the counterweightcarrier in a first direction; and a second actuator linked to thecounterweight carrier, for moving the counterweight carrier in a seconddirection, opposite to the first direction.
 2. The telescoping cameracrane of claim 1 where the first and second actuators each comprise ahydraulic actuator.
 3. The telescoping camera crane of claim 1 furtherincluding a first actuator pulley on the first actuator and a firstidler pulley on the first section, with a first cable extending aroundthe first actuator pulley and the first idler pulley, and a secondactuator pulley on the second actuator and a second idler pulley on thefirst section, and with a second cable extending around the secondactuator pulley and the second idler pulley.
 4. The telescoping cameracrane of claim 1 further including: a third section extendible from thesecond section; a camera platform pivotably attached to a front end ofthe third section; and a leveling system linked to the camera platform.5. A camera crane comprising: a first tube; a second tube extendiblefrom the first tube; a third tube extendible from the second tube; acounter weight moveable relative to the first tube; and a pair ofopposing hydraulic actuators adapted for directly or indirectly movingthe counter weight and at least one of the second tube and the thirdtube.
 6. The camera crane of claim 5 with the hydraulic actuatorsattached to a top surface of the first section and with each hydraulicactuator linked to counterweight carrier by a cable passing around afixed idler pulley.
 7. A telescoping camera crane comprising: a firstsection; a counter weight carrier moveable along the first section; asecond section linked to the counter weight carrier; a third sectionextendible from the second section; a camera platform supported by thethird section; an actuator linked to the counter weight carrier; and astop position system on the first section and engageable by the counterweight carrier, for controlling the actuator to stop the third sectionat a selected position.
 8. The telescoping camera crane of claim 7 wherethe actuator comprises a hydraulic cylinder, and the stop positionsystem includes at least one cam on the first section moveable via acounter weight tray to engage a shutoff valve, to stop flow of hydraulicfluid to the hydraulic cylinder.
 9. The telescoping camera crane ofclaim 8 with the stop position system including a front bar and a rearbar slidable on the first section, a spring connecting the front bar andthe rear bar, and with each bar including a cam engageable to a shutoffvalve.
 10. The telescoping camera crane of claim 7 further includingstop position adjustment means for adjusting the stopping position ofthe third section.
 11. A telescoping camera crane comprising: a firstsection; a counter weight carrier moveable along the first section; asecond section linked to the counter weight carrier and telescopicallyextendible out of the first section; a third section telescopicallyextendible from the second section; a camera platform supported by thethird section; an actuator for driving telescopic movement of the secondand third sections; a camera platform leveling system including at leastone cable linked to the camera platform, to keep the camera platformlevel; and a cable tensioning system acting on the at least one cable tocompensate for backlash in the leveling system.
 12. The telescopingcamera crane of claim 11 wherein the actuator comprises a hydraulicactuator driven via a hydraulic system, and where the cable tensioningsystem includes at least one stabilizer assembly acting to tension theat least one cable, and with the cable tensioning also driven via thehydraulic system.
 13. The telescoping camera crane of claim 11 with thecamera platform leveling system comprising a first leveling cableconnecting to the camera platform, and extending around a levelingroller on the second section and connecting to a leveling axle pivotablysupported on the first section, and with a second leveling cableattached to the leveling axle and to the center post, and with the cabletensioning assembly positioned to deflect the second levelling cable.14. A telescoping camera crane comprising: a first section; a counterweight carrier moveable along the first section; a second sectiontelescopically extendible out of the first section; a third sectiontelescopically extendible from the second section; a camera platformsupported by the third section; an actuator for driving telescopicmovement of the second and third sections; a camera platform levelingsystem linked to the camera platform, to keep the camera platform level;and tensioning means for keeping the camera platform levelnotwithstanding backlash in the camera platform leveling system.